The Total Harmonic Distortion (THD) analyzer is the most widely used instrument for evaluation of distortion in analog signal processing equipment. A nonlinearity in a unit under test (UUT), when adequately excited by a sinusoidal wave (the fundamental) will produce, at an output of the UUT, the fundamental sinusoid along with harmonics of the fundamental sinusoid wave. The THD analyzer measures the magnitude of the harmonics to objectively describe the nonlinearity in the UUT.
Because the THD analyzer works by generating a sinusoid to input into the UUT and then removing the same sinusoid from the signal output from the UUT, it is necessary to have a uniform reference signal to produce a standardized result. Comparing the performance of THD analyzers cannot be done without a uniform input signal.
What is needed in the art, thus, is a signal generator to provide a standard reference sinusoid.